This invention relates to a process for treating a waste water containing uranium and fluorine. More particularly, it relates to a process for efficiently removing or decreasing uranium and fluorine in a waste water produced in conversion step of natural or depleted uranium into uranium hexafluoride or in reconversion step of uranium hexafluoride from enriched or depleted uranium into uranium oxide.
FIG. 4 shows an example of a wet process for converting a yellow cake into uranium hexafluoride, in which a waste water containing uranium and fluorine is produced. In this process, a waste liquor for washing a solvent by carbonate, a condensate from an acid recovery columm, a waste liquor for washing UF.sub.4 crystals and a scrubber waste liquor are generated as shown in FIG. 4. The following Table shows the typical compositions and amounts of these waste liquors.
______________________________________ Condensate Waste liquor from acid for washing Waste liquor Scrubber recovery solvent by for washing waste Item column carbonate UF.sub.4 crystals liquor ______________________________________ pH .ltoreq.1 7-8 6-8 9-11 F 1.0-3.0 g/l -- 100 mg/l 5.0 g/l U 20 mg/l 3 mg/l 100 mg/l -- HCl 2.0-11.0 g/l -- -- -- HCO.sub.4 -- 10 g/l -- -- Amount 50 m.sup.3 /day 50 m.sup.3 /day 24 m.sup.3 /day 2 m.sup.3 /day ______________________________________
Usually these waste liquors are combined together, treated as a waste water containing uranium and fluorine to thereby lower the concentrations of the uranium and fluorine below the levels defined by the regulation under the law, and then discharged into a river or the like.
Conventional processes for treating a waste water containing uranium and fluorine include solid-liquid separation by neutralizing precipitation and adsorption with ion exchange resins.
However the solid-liquid separation by neutralizing precipitation as described above has a disadvantage that the levels of the uranium and fluorine in the waste water can not be satisfactorily lowered, which makes it necessary to sufficiently dilute the supernatant thus obtained with water prior to discharge thereof. On the other hand, the adsorption with ion exchange resins is superior to the former process in the removal of the uranium and fluorine. However it has some disadvantages that it is necessary to frequently regenerate these resins or to employ large resin columns when the waste water contains these ions at high concentrations; and that it is accompanied by the formation of waste liquors to be treated, i.e., eluates of the ions and washings for the resins.